ip route command

[rhltechie]

Hi All,

Can someone tell me the difference between doing the following:

ip route 10.0.0.0 255.255.255.0 FastEthernet1/0

and

ip route 10.0.0.0 255.255.255.0 10.0.0.1

I did the first one on my router to begin with and it did not work, but the second did. What is the differnce between using the next hop address and the outgoing interface?

TIA,

R

[devang_etcom]

when you configure the static route using the nexthop then it will have entry in the routing table with the AD of 1 same as

ip route 10.0.0.0 255.255.255.0 10.0.0.1

and when you configure the static routes using the interface then it will have entry in the routing table as directly connected same as

ip route 10.0.0.0 255.255.255.0 fast ethernet 1/0

and i think it is more preferable than the path with AD of 1

hope this will help you

rate this post if it helps

regards

Devang

[vladrac-ccna]

Difference is bigger than that.

When you have a static route using interface, your router will believe 10.0.0.0 255.255.255.0 is directly connected to your router. so it will use ARP to reach this network. If you have another router (and not a multiaccess media) you'll need proxy-arp to make this work.

If this is not clear let us know,

vlad

[Richard Burts]

Many people believe, as Devang suggests, that there is a difference in Administrative Distance of static routes that specify next hop or static routes that specify outbound interface. But this is not true. Both types of static routes have the same administrative distance of 1.

Vlad's comment about proxy ARP is partly true. If the static route points to a point to point interface (such as HDLC or PPP) then there is no need for ARP and the router just forwards out the interface. If the static route points to a broadcast interface then the router will need to ARP, and the neighbor will need to have proxy ARP enabled for it to work.

There are two implications of this point that make static routes specifying outbound interface over broadcast interface not good practice. The first implication is that the successful operation of our router is now dependent on how some other device is configured. (and a number of organizations are disabling proxy ARP as part of their security posture). The other implication is that the router will need to ARP for EVERY destination host address. This will increase the load on the CPU and will lead to quite large ARP tables (consuming more memory to hold the ARP table and requiring more CPU resources to maintain the table).

So a static route specifying outbound interface of point to point interface is fine. Otherwise the best practice is to do static routes specifying next hop address.

HTH

Rick